The kinetics and the mechanism of the catalytic reduction of nitrogen oxide
s (NOx) by hydrogen were studied over a modified alumina-based palladium mo
nolith. Nitrogen, nitrous oxide, ammonia, and water were detected as reacti
on products. Transient experiments yielded information about the surface re
action mechanisms. The dissociation of NO is the crucial step, dominating t
he overall reaction behaviour and that it depends on temperature and on the
partial pressure of H-2. A transient kinetic model based on elementary rea
ction steps was developed for a stoichiometric mixture of (NO + H-2)/Ar. Th
e model was based on the transient plug flow concept. The parameters of mod
el were determined by regression analysis. The comparison of model simulati
ons with the experimental data revealed that the model was able to describe
the transient NO reduction kinetics. (C) 2001 Published by Elsevier Scienc
e Ltd.